Heart disease is the leading cause of death for both men and women in the US, accounting for nearly 40% of all annual deaths. A high cholesterol level is well-known risk factors for heart disease. Although blood cholesterol can be lowered using a number of marketed drugs, of which statins are the leading drugs, only 38% of patients taking these drugs are achieving the low-density lipoprotein cholesterol goals set by the National Cholesterol Education Program (NCEP). Furthermore, patients with homozygous familial hypercholesterolemia who have markedly elevated cholesterol levels respond poorly to current drug therapy, and are at very high risk of premature cardiovascular disease. These and other patients will dramatically benefit from an aggressive treatment of hypercholesterolemia. The long-term goal of this work is to develop novel drugs for cholesterol lowering. Our therapeutic target is the protease proprotein convertase subtilisin-like kexin type 9 (PCSK9). PCSK9 controls the degradation of the LDL receptor (LDLR) in the liver and thereby contributes to cholesterol homeostasis. PCSK9 is synthesized as a precursor protein that undergoes processing between the prodomain and catalytic domain. This processing is required for PCSK9 to be secreted and to undertake its biological activity. Our goal is to identify compounds that prevent the processing of PCSK9, thus prevent its secretion and its ability to participate in the degradation of the LDL receptor. To achieve our Phase I goal, we have integrated virtual (computer) screening methods with cell-based assays and consequently identified five screening hits. As part of this Phase II proposal, we plan to expand and optimize our hits, and confirm the ability of selected compounds to stabilize the LDLR and decrease the LDL-C level using in situ and in vivo studies. PUBLIC HEALTH RELEVANCE: Heart disease is the leading cause of death for both men and women in the US. A high cholesterol level is a well-known risk factor for heart disease. Although blood cholesterol can be lowered using a number of marketed drugs, these drugs do not treat a segment of the population with very high cholesterol. Our goal is to develop new cholesterol lowering drugs that have an effect on all individuals with high cholesterol levels, including that segment of the population having very high cholesterol levels.